ZeaChem Proves Key Step - Pilot Plant Due Online This Year
The ZeaChem process goes something like this (illustrated in the above diagram):
- Woody biomass (e.g. hard- and softwood, grasses, corn stover, etc.) goes in one end.
- That woody stuff gets chemically separated into two groups: sugars and “everything else.”
- The sugars are sent to a fermentation tank where, using nothing but already existing and proven microbes, they are fermented into acetic acid. A key benefit of this type of fermentation over traditional fermentation with yeast that you see in corn ethanol facilities is that it produces no carbon dioxide. Yeast fermentation produces one molecule of CO2 for every molecule of ethanol. You can see the problem there.
- The resulting acetic acid then goes through a process called esterification to convert it to ethyl acetate.
- The residue of “everything else” that is left over from the initial chemical separation is then gasified and turned into hydrogen and other syngases.
- The hydrogen is then combined with the ethyl acetate to make ethanol in a process called hydrogenation.
- The other syngases are burned to generate the necessary steam and electricity needed to run almost the entire process from beginning to end.
Now that ZeaChem has proven its esterification step it is ready to set up its pilot plant sometime before the end of 2010. The company has an advantage over most other biofuels companies in that its key intermediate -- ethyl acetate -- is itself a valuable chemical on the market, and could be sold instead of ethanol, should the market dictate.
Now we will see which approach for producing ethanol from cellulose is best: ZeaChem's indirect path, the direct to ethanol fermentation, or the gasification to fermentation approach favoured by Coskata.
Labels: cellulosic fuels